Method of making plastic coal briquetts

ABSTRACT

A method of making plastic coal briquettes wherein initial coal (either a gas coal or a mixture of a gas coal and a poorly caking coal) is heated up to a softening temperature and subsequently cured under approximately isothermal conditions. Pressure forming is then effected in two stages during the first stage a coal strip of which the thickness is not less than the required thickness of a final product, i.e. of a briquette, is pressure formed while during the second pressure forming stage plastic coal briquettes are produced from this strip. The method produces coal briquettes from gas coals and mixtures of gas coals with poorly caking coals in a high-capacity production line.

United States Patent [191 Grechanichenko et a1.

[451 Dec. 24, 1974 METHOD OF MAKING PLASTIC COAL BRlIQUETTS [76] Inventors: Grigory Mikhailovich Grechanichenko, Pushkinsky viezd, 7, kv. 16; Evgeny Savelievich Gusinsky, ulitsa Lopanskaya, 34; Anatoiy Semenovich Petrukhno, ploschad Rozy Ljuxemberg, 5, kv. 26; Evgeny Vladimirovich Dobrovolsky, Pushkinsky viezd, 7, kv. 8, all of Kharkov, U.S.S.R.

[22] Filed: Nov. 21, 1973 [21] Appl. No.: 418,036

[52] US. Cl. 44/10 H, 44/15 R [51] Int. Cl. C1015/00, C101 5/10 [58] Field of Search 44/2, 10 1-1, 11-13,

[56] References Cited UNITED STATES PATENTS 3,663,186 5/1972 Dzhaparidze et a1. 44/10 H Schmalfeld et a1. 44/10 R Holowaty 44/13 [57] ABSTRACT A method of making plastic coal briquettes wherein initial coal (either a gas coal or a mixture of a gas coal and a poorly caking coal) is heated up to a softening temperature and subsequently cured under approximately isothermal conditions. Pressure forming is then effected in two stages during the first stage a coal strip of which the thickness is not less than the required thickness of a final product, i.e. of a briquette, is pressure formed while during the second pressure forming stage plastic coal briquettes are produced from this strip. The method produces coal briquettes from gas coals and mixtures of gas coals with poorly caking coals in a high-capacity production line.

2 Claims, 1 Drawing Figure METHOD OF MAKING PLASTIC COAL BRIQUIETTS BACKGROUND OF THE INVENTION The present invention relates to coke-chemical technology and, more particularly, it relates to methods of making plastic coal briquetts.

Coal briquetts are used for the production of formed blast-furnace coke.

A variety of methods of making coal briquetts by a hot brick-forming technique are known in the art, according to which an initial coal mixture is formed while hot without the use of a binding agent. A disadvantage of these known methods is that they cannot be employed for making coal briquetts for subsequent production of blast-furnace coke, when the initial coal is characterized by poor caking (such as gas coals, Internationally Classified as Types 71 1 and 721 as well as when the initial coal mixture includes gas coals and poorly caking coals (coals Internationally Classified Type 41 l The known method necessitates the addition of a quantity of expensive caking coals to the coal mixture, as one of the components.

Methods are also known of making coal briquetts from poorly caking coals and from mixtures containing gas coals and poorly caking coals without a binding agent, according to which coal is heated and cured under approximately isothermal conditions, until a desired degree of thermal destruction of the coal is attained, whereafter the coal is pressure formed in a separate apparatus.

A disadvantage of the above known methods is the impossibility of attaining a required degree of destruction of the coal maintained under approximately isothermal conditions, on account of the eventual aggregation of the coal, whereby destruction is completed directly during the process of forming the plastic stock, i.e., during the briquette-forming stage.

The above disadvantage results in increased briquette-forming time, which means that the productivity ofthe briquette production line becomes relatively low.

Furthermore, a method is also known of making plastic coal briquetts from gas coals and poorly caking coals by pressure forming in a single stage.

A disadvantage of this last-mentioned known method is the need to keep the briquette under pressure for a relatively long time, as long as 8 to seconds, in order to create conditions for development in the coal of the processes for thermal destruction, which consumes time and results in low productivity.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above disadvantages.

It is an object of the present invention to provide a method which produces plastic coal briquetts usable for subsequent production of formed blast-furnace coke from gas coals and poorly caking coals and which is operable in a high-productivity production line.

These objects are attained in a method of making plastic coal briquetts from gas coals and poorly caking coals, wherein the coals are heated up to a softening temperature. The heated coal is then cured under approximately isothermal conditions and then is pressure formed, in which method, in accordance with the present invention, pressure forming of the heated coal is peformed in two stages. In the first stage a plastic coal strip is formed, the thickness of which is not less than the required thickness of the briquetts to be made and during the second stage plastic coal briquetts or pellets are pressure formed from this strip.

In accordance with a preferred embodiment of the invention, the plastic coal strip is formed under a pressure of 2 to 15 kg/cm for 5 to 15 seconds, and the briquettes or pellets are formed under a similar pressure in 0.05 to 0.4 seconds.

The method of the invention produces coal briquetts for subsequent production of formed blast furnace coke gas coals and mixtures of gas and poorly caking coals (the types of such coals are, respectively, Internationally Classified Types 71 1, 721 and 41 1 characterized by poor caking and capable of attaining a plastic state only for short periods. Furthermore, this method produces such coal briquetts in a high-productivity production line.

This is attained (and that without the use of binding agents) by utilizing the limited inherent caking properties of these coals, by means of controlling the processes of destruction, synthesis and polycondensation of the organic substance of the coals, which result in the appearance of a plastic phase, in forming of gas non-permeability of the plastic coal stock and which provide for producing briquetts and producing formed blast-furnace coke of sufficiently homogeneous structure.

In accordance with another feature of the present invention, the initial coal (i.e, either gas coals or a mixture of gas and poorly caking coals) is predesintegrated to a state in which about per cent of the entire coal stock has a particle size of 3 mm, whereafter the stock is heated to a temperature for softening this coal.

The duration of the heating step is as has been found, shorter than the time required for development in the coal, of the process of thermochemical destruction.

To provide for this condition, the temperature of the ambient air in which the heated coal is cured is not lower by more than to C than the softening temperature of a given type of the coal.

Then the coal is subjected to pressure forming in two stages.

During the first stage the coal is subjected to a pressure within a range from 2 to 15 kg/cm under approximately isothermal conditions, with consequent production of a plastic coal strip of a thickness approximating the required thickness of the briquettes. During this stage the processes of destruction, synthesis and polycondensation of the organic substance are developed and completed within the coal and also completed is the formation of the plastic coal stock.

The thus formed plastic coal stock is used the second stage for the pressure forming therefrom of individual briquetts under a similar pressure of 2 to ISkg/cm in 0.05 to 0.4 seconds.

It has been found that when the coals used are maintained under the above described conditions prior to the application of pressure and during the application of pressure, for a time insufficient for a given type of coal or coal mixture, the processes requiring the formation of a plastic stock are not, whereas when the coals are maintained under the above described conditions for a time which is too long, certain processes are developed in the structure of the coal which result in brittleness.

In both cases the quality of the formed coke is affected (the coke becomes fragile), and the percentage of moulded waste increases.

If the applied pressure is insufficient for a given type of coal or for a given coal mixture, the strength of the plastic coal briquettes obtained is reduced, so that they may be partly destroyed during subsequent transportation, handling and thermal treatment, thus increasing the percentage of waste. On the other hand, if the applied pressure is too high, the briquettes and the formed coke produced therefrom are characterized by insufficient porosity, which affects the performance of the formed coke in a blast furnace.

BRIEF DESCRIPTION OF THE DRAWINGS The appended drawing shows a general diagram for the realization of the method of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The coal a heated to a softening temperature is fed in a fluent state into an apparatus 1 wherein it is held for a given period without the application of pressure under approximately isothermal conditions. The duration of this holding period depends on the character of the coal being treated. The apparatus 1 may have any suitable known structure, e.g., is may be a screw conveyor, a plate-type conveyor, etc.

The coal is forwarded from the apparatus 1 into a pressure forming apparatus 2 wherein it is subjected to the first forming stage and where it is reduced from the fluent state into a plastic coal strip. The duration of the pressure forming, i.e., the exposure to pressure and the pressure value are selected in accordance with the type of coal being treated.

The pressure forming apparatus 2 may be of any suitable known structure, e.g., it may be a continuousaction forming press.

The plastic coal strip is forwarded from the pressureforming apparatus into a briquette froming apparatus 3 where it is subjected to the second pressure forming stage, i.e., to re-moulding into coal briquettes B. The briquette forming apparatus 3 may be of any suitable known structure, e.g., it may be a briquette-forming press, the size and volume of the briquettes B being selected to correspond to the requirements of production of formed blast-furnace coke.

All the described apparatus may be structurally combined into a single machine.

From the pressure forming apparatus 3 the plastic coal briquettes are forwarded into baking ovens for producing formed blast-furnace coke.

The method of the present invention has been tested in an experimental industrial plant by producing thousand tons of plastic coal briquettes from inexpensive gas coals and mixtures of gas coals and poorly caking coals of different grades which are otherwise nonutilizable for the production of blast-furnace coke. The coke produced from these briquettes has been used in an operating industrial blast furnace.

EXAMPLE 1 A gas coal (Internationally Classified as Type 71 1 is treated. The coal is pre-heated to a temperature of 452C and cured at an ambient temperature within the range of 300 to 350C for 50 seconds 1 minute without the application of pressure, whereafter the coal is pressure formed for 10 to 15 seconds under a pressure within the range from 2 to 3 kg/cm into a plastic coal strip 60 mm thick. This coal strip is subsequently re-formed under a pressure from 8 to 10 kg/cm into pillow-shaped pellets 35 to 40 mm thick.

The briquettes are subjected in a heated state to a thermal treatment (i.e., to heating up to 800 850C) to remove the volatile substances, whereby formed blast-furnace coke is obtained having a volatile content below 1.5 percent and such characteristics as M. about and M about 6.5 7.0 percent. This coke ensures reduced coke consumption during iron making and increases productivity of the blast furnace, compared with the use of coke produced from caking coals by the traditional method of layer-wise coking in batch ovens.

EXAMPLE 2 A mixture containing 60 per cent gas coal (Interna tionally classified as Type 721 and 40 per cent poorly caking coal (Type 41 l) is treated. The mixture is heated to a temperature of 460 1*: 4C and cured at ambient temperature from 350 to 400C for 30 i 2 seconds, whereafter it is subjected to a pressure of 5 6 kg/cm for 6 to 8 seconds, with consequent production of a plastic coal strip 40 to 50 mm thick. This strip is re-formed under a pressure of 10 kg/cm into pillowshaped plastic briquettes with dimensions 62 X 62 X X 35 mm. The briquettes are thermally treated in a hot state to removed the volatile substances, whereby formed blast-furnace coke is obtained with volatile content below 1.5 percent and characteristics M, about 90 percent and M about 7 percent. This coke ensures during iron making reduced coke consumption and increased capacity of the blast furnace, as compared with the use of coke produced from caking coals by the traditional method of layer-wise coking in batch ovens.

What is claimed is:

I. A method of making plastic coal briquettes from gas coals and poorly caking coals, comprising the steps of: heating the coals to a softening temperature thereof; maintaining the heated coals under approximately isothermal conditions; pressure forming a plastic coal strip having a thickness which is not less than the required thickness of a plastic coal briquette to be made from the heated coals; pressure forming individual plastic coal briquettes from the pressure formed coal strip.

2. A method of making plastic coal briquettes, as claimed in claim 1, wherein said plastic coal strip is formed at a pressure within a range from 2 to 15 kg/cm for 5 to 15 seconds, while the step of pressure forming individual plastic coal briquettes is effected under a similar presure for 0.05 to 0.4 seconds. 

1. A METHOD OF MAKING PLASTIC COAL BRIQUETTES FROM GAS COALS AND POORLY CAKING COALS, COMPRISING THE STEPS OF: HEATING THE COALS TO A SOFTENING TEMPERATURE THEREOF; MAINTAINING THE HEATED COALS UNDER APPROXIMATELY ISOTHERMAL CONDITIONS; PRESSURE FORMING A PLASTIC COAL STRIP HAVING A THICKNESS WHICH IS NOT LESS THAN THE REQUIRED THICKNESS OF A PLASTIC COAL BRIGUETTE IS BE MADE FROM THE HEATED COALS; PRESSURE FORMING INDIVIDUAL PLASTIC COAL BRIQUETTES FROM THE PRESSURE FORMED COAL STRIP.
 2. A method of making plastic coal briquettes, as claimed in claim 1, wherein said plastic coal strip is formed at a pressure within a range from 2 to 15 kg/cm2 for 5 to 15 seconds, while the step of pressure forming individual plastic coal briquettes is effected under a similar presure for 0.05 to 0.4 seconds. 